The proposed research is designed to study the mechanism of DNA replication using bacteriophage infected E. coli as a model system for the investigation with emphasis on the investigation of the initiation process. One of the initiation proteins, T4 39- protein, which has been defined genetically as needed for the initiation process, and has been found to be membrane associated and DNA-binding, will be purified to apparent homogeneity. The purified 39- protein will be characterized biochemically with regard to its role as the linkage bacterial membrane and T4 DNA replication. Since the 39- protein of T2, T4 and T6 is nonhomologous, we will include a comparative study of the 39-protein of the three T-even phages and their effect on homologous and heterologous DNA replication as a means to study the control and selectivity of DNA replication.